If you're not sure of something, try it! Here's my take, though it has not been tested.
Other people made good suggestions, my example is the requirement reduced to the absolute minimum. I used RSECT rather than CSECT for two reasons.
- RSECT implies that the CSECT is read only, and the Assembler applies the same tests as specifying RENT.
- The read only attribute is carried into the load module. No verification is done, but it's there.
The read only attribute is used when linking the z/OS nucleus. The nucleus loader (which is part of the IPL procedure) uses it, but I no longer recall how it's used. Not that any of us are going to relink the nucleus. It's been 30 years, probably longer, since I've done it.